The present invention relates generally to the field of electric utility meters. More particularly, the present invention relates to both electronic watthour meters and meters utilized to meter real and reactive energy in both the forward and reverse directions.
Techniques and devices for metering the various forms of electrical energy are well known. Meters, such as utility power meters, can be of two types, namely, electro-mechanical based meters whose output is generated by a rotating disk and electronic based meters whose output component is generated electronically. A hybrid meter also exists, wherein an electronic register for providing an electronically generated display of metered electrical energy has been combined, usually optically, to a rotating disk. Pulses generated by the rotating disk, for example by light reflected from a spot painted on the disk, are utilized to generate an electronic output signal.
It will be appreciated that electronic meters have gained considerable acceptance due to their increasing reliability and extended ambient temperature ranges of operation. Consequently, various forms of electronic based meters have been proposed which are virtually free of any moving parts. In the last ten years several meters have been proposed which include a microprocessor.
Testing of electronic meters has always been a problem. A special mode of register operation known in the industry as the test mode has been available to ease register testing, however, little has been done to improve overall meter testing. Electronic meters have the potential of providing faster test times, multiple metering functions and calibration of the meter through software adjustment. However, implementing such functions can be expensive and complicated.
Presently, electric utility companies can test mechanical meters with a piece of test equipment which can reflect light off a metered disk to detect a painted spot as the disk rotates. An alternative form of testing mechanical meters is disclosed in U.S. Pat. No 4,600,881xe2x80x94LaRocca et al. which describes the formation of a hole in the disk. A light sensitive device is placed in a fixed position on one side of the disk. As the disk rotates, and the hole passes over the light sensitive device, a pulse is provided indicating disk movement.
Since electronic meters preferably do not contain rotating disks, such simple testing techniques cannot be utilized. Consequently, a need exists for an electronic meter having a relatively simple means of testing the meter.
The previously described problem is resolved and other advantages are achieved in a method and apparatus for electronically displaying metered electrical energy are disclosed. A first processor receives voltage and current signals and determines electrical energy. The first processor generates an energy signal representative of the electrical energy determination. A second processor, connected to said first processor, receives the energy signal and generates a display signal representative of electrical energy information. A display is connected to receive the display signal and displays the electrical energy information. In a first embodiment it is preferred for the first processor to determine units of electrical energy from the voltage and current signals and to generate an energy signal representative of such units and the rate at which the units are determined. In this embodiment it is also preferred for the second processor to generate, in response to the energy signal, a disk signal representative of a rate of disk rotation equivalent to a traditional electromechanical meter and display signals are representative of the total number of units, the rate at which units are determined and the rate of equivalent disk rotation, wherein the display includes separate indicators for each display signal. In another embodiment the first processor, in concurrently determining units of electrical energy, determines watt units, apparent reactive energy units and the rate at which such units are determined, wherein the watt units, the apparent reactive energy units and the rate at which such units are determined are displayed. In still another embodiment, the first processor meters multiple types of electrical energy and generates energy signals. A first converter is provided for converting an electrical output signal to light. The second processor, connected to the first converter, generates an output signal in response to the energy signals, wherein the generation of the output signal includes the multiplexing of the energy signals into the output signal. In a still further embodiment, the display provides energy flow direction information.
It is preferred for the display to be a liquid crystal display containing a plurality of visible annunciators. It is especially preferred for the second processor to generate the display signal so that select annunciators are made visible at select times. In this fashion it is possible to provide an energy usage indicator equivalent to that of a rotating disk. It is especially desirable for the display signal to be generated so that the annunciators provide a forward and reverse energy flow indication at a rate faster than an equivalent disk rotation rate. In an especially preferred embodiment, three annunciators are located on the display for providing the above indications of electrical energy direction. In that embodiment, the annunciators are arranged in a line. The first annunciator is arrow shaped and indicative of the reverse direction and the third annunciator is arrow shaped and indicative of the forward direction. It is also preferred for the energy signal to be provided to the second processor at a given data rate. In such an embodiment it is especially preferred for the second processor to include a data rate display member for displaying on the display the rate at which data is being provided to the second processor. In such an embodiment, the direction and both the rate at which data is provided to the second processor and a signal mimicking the rate of disk rotation can be displayed. Indicators for each quantity are provided.